1. Field of the Invention
The field of art to which this invention pertains is electrostatic speakers and in particular to means for biasing the speakers to use only a single voltage source and also to constructional means for supporting and mounting the individual transducer units of the speaker.
2. Description of the Prior Art
In general, electrostatic transducers have been limited with respect to power output capability, particularly in the lower range of frequency response, because of narrow spacing between the active elements thereof. With the given spacing, only a given voltage may be applied due to breakdown of the air dielectric, and thus a limit to the force which can be developed is established.
Application of this class of transducer has therefore been limited to designs that can accept this limitation. In particular, this limitation is more noticeable at low audio frequencies, since it is desirable to totally enclose the back of the speaker with a reasonably sized enclosure, and this in turn implies that high forces be developed to move the diaphragm against the air loading.
The foregoing will be more apparent in considering a system, by way of example, for converting audio frequency electrical energy into acoustical energy. It is axiomatic in the art that equal power output over the audio frequency range a much greater mass of air must be moved at the lower frequencies and it is the reason that low frequency loudspeakers are much larger and more heavily constructed than high frequency loudspeakers. In any case, the low power output limitation is the result of the limited maximum excursions demanded of the flexible diaphragm.
In order to solve the above problems, Brettel has developed a new electrostatic transducer as described in his U.S. Pat. No. 3,136,867 (issued June 9, 1964).
According to Brettel's transducer, it is required to provide two kinds of D.C. voltage sources in order to drive both diaphragms in the same direction. Generally, since it is required high voltage for bias, it is not wished to provide two kinds of sources.